Much of the global economy depends on petroleum products, the price of which can be very volatile depending on political and economic conditions. This volatility creates a number of issues, including economic issues and national security issues. As a result, many have been searching for and developing alternative forms of energy, such as by improving current methods of extracting energy from coal, wind, and the sun. Biological material has also been identified as a promising source of energy. For example, oil palm and jatropha plants are known to produce seeds with high percentages of oil that can be extracted and refined for fuel.
One promising biological source of oil involves the harvesting of certain species of algae that produce large amounts of oil that can be extracted. Predictions have been made that using harvesting oil from algae can yield amounts of energy several times greater than what is possible using other organisms. Despite these theoretical predictions, the harvesting of algae has yet to become economically viable because the price of harvesting algae has not yet reached a level comparable to other forms of energy. Some of the problems with harvesting algae are caused from the fact that algae typically grows in water and creates stored energy in the form of oil through the process of photosynthesis. As a result, algae tends to float to the surface of bodies of water in which it is grown, thereby causing algae near the surface to grow well whereas algae below the surface do not grow well because they do not have enough sunlight. Consequently, oil yield per unit area typically depends on the surface area of the bodies of water used to grow the algae and much of the volume of the water below the surface is essentially wasted.